It depends on the recipe. Actually, in most cases, you can simply divide or multiply a recipe (best when halving or doubling... going up 16x can lead to problems). What isn't so easy is adjusting cooking times.

For a bread like this - it works pretty well to just divide all the ingredients in half. The yeast is the trickiest part as measuring out 3.5 g of yeast is difficult without scale accurate to 0.1 g. If you end up with a tad less yest, it's okay - rise times will need to increase. Too much and rise times should be reduced.

Depending on how it's supposed to be baked, the baking times make not need any adjustment.

well, it just needs to be for 45minutes and need to be risen twice. once without the olives added and once with the olives added. I have made this full recipe and no problem. it turns out great. but because i will be trying to use a toaster oven(small). it won't fit.

Baking time will probably need to be adjusted. This will be completely dependent on your toaster oven and then pan (both shape and color make huge differences) you will be using and it will be hard to predict. First time you do this, start checking at 30 min and then every 5 min after that. When you reach the suitable "done" point, remember that time and next time you bake the same recipe in the same toaster oven start checking 5 minutes before that as verification.

Toaster ovens are often poor at providing even baking temperatures throughout the volume of the oven as well as through the baking process, so your bread might not come out as nice as with a larger oven. However, most toaster ovens have a light and glass window which lets you visually check the status of the bread without opening the door. Every time the door is opened there is significant heat loss that will extend the baking time (making the time recorded inaccurate for future use - but a good guide; that's why I recommend using that only as a starting value for future baking where you can continue to refine the baking time for your particular setup).

As for rise times, volume increases are what we're looking for, but in most cases the same rise time produces the same amount of rise. For example, if your dough takes 3 hours to double in volume, usually a halved recipe will also take 3 hours to double. But, keep in mind that a half packet of yeast is hard to control - so you may need to extend or be able to shorten your rise times.

A packet of yeast contains 2 1/4 teaspoons, so you'll need 1 1/8 teaspoons if you halve the recipe. But like Michael said, a little more/less yeast isn't going to mess up your bread--it's just going to shorten/lengthen the rising time.

That said, my initial thought was why go to all the trouble for a little bit of bread? You can make the recipe with the quantities specified, and then divide it in half when it is ready to rise. Put one half in the refrigerator to slow down the rising process long enough to get the first loaf baked off before the second loaf is ready to bake. If you pull the dough out of the frig when the room temperature dough is ready to shape, that should buy you more than enough time.

Sometime it's hard to make a smaller portion. My mom is the living proof. When she was younger, she was always making portions for 6 people, when she got married and moved away, now shes making the same portions but for 4 of us. Each day I'm telling her that it's too much, but after 20 years, she still continues with her own way.

If you ask me, I'd say use math. Make everything proportional and with amount of ingredients you'll be accurate, just I'm no chef so maybe in practice math wont do